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−### Copyright (C) 1996 John W. Eaton
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−###
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−### This file is part of Octave.
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−###
+
−### Octave is free software; you can redistribute it and/or modify it
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−### under the terms of the GNU General Public License as published by
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−### the Free Software Foundation; either version 2, or (at your option)
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−### any later version.
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−###
+
−### Octave is distributed in the hope that it will be useful, but
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−### WITHOUT ANY WARRANTY; without even the implied warranty of
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−### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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−### General Public License for more details.
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−###
+
−### You should have received a copy of the GNU General Public License
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−### along with Octave; see the file COPYING.  If not, write to the Free
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−### Software Foundation, 59 Temple Place - Suite 330, Boston, MA
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−### 02111-1307, USA.
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−
+
−## usage: polyval (c, x)
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−##
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−## Evaluate a polynomial.
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−## 
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−## In octave, a polynomial is represented by it's coefficients (arranged
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−## in descending order). For example a vector c of length n+1 corresponds
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−## to the following nth order polynomial
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−## 
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−##   p(x) = c(1) x^n + ... + c(n) x + c(n+1).
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−## 
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−## polyval(c,x) will evaluate the polynomial at the specified value of x.
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−## 
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−## If x is a vector or matrix, the polynomial is evaluated at each of the
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−## elements of x.
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−## 
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−## SEE ALSO: polyvalm, poly, roots, conv, deconv, residue, filter,
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−##           polyderiv, polyinteg
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−
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−function y = polyval (c, x)
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−
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−  ## Written by Tony Richardson (amr@mpl.ucsd.edu) June 1994.
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−
+
−  if (nargin != 2)
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−    usage ("polyval (c, x)");
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−  endif
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−
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−  if(is_matrix (c))
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−    error ("poly: first argument must be a vector.");
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−  endif
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−
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−  if (length (c) == 0)
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−    y = c;
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−    return;
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−  endif
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−
+
−  n = length (c);
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−  y = c (1) * ones (rows (x), columns (x));
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−  for index = 2:n
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−    y = c (index) + x .* y;
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−  endfor
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−
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−endfunction